1. Field of the Invention
The present invention relates to a structure which can be used in reactions wherein the reaction and distillation of the reaction system are carried on concurrently using the structure as both catalyst for the reaction and as a distillation structure.
2. Related Art
Recently a new method of carrying out catalytic reactions has been developed, wherein the components of the reaction system are concurrently separable by distillation, using the catalyst structures as the distillation structures. This method is now generally known as catalytic distillation and any reference to catalytic distillation herein will be taken to mean this method or process. Such systems are described variously in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,302,356; 4,307,254; 4,336,407; 4,439,350; 4,443,559; and 4,482,775. U.S. Pat. No. 4,447,668 discloses the dissociation of ethers in a catalytic distillation column. In addition, U.S. Pat. Nos. 4,443,559 and 4,250,052 disclose a variety of catalyst structures for this use.
Sulzer European Pat. No. 0396650 discloses a catalytic distillation structure comprising semirigid mesh like walls containing catalyst material and formed into channels which are layered together such that the flow of the channels cross. Sulzer U.S. Pat. No. 4,731,229 discloses a similar packing. Other Sulzer distillation packings are shown in U.S. Pat. Nos. 4,455,339; 4,497,751; 4,497,752; 4,744,928 and 4,497,735 and UK patents 1,471,442; 1,569,828 and 1,186,647. The present invention provides a catalytic distillation structure for use in reactions, which can be used as a distillation structure. In order to serve both functions, it has been found that the structure must meet three criteria. First, the structure must be such as to provide for even spatial dispersement in the reactor distillation column. That is, the catalyst structures must rest in the column in a geometric arrangement which will perform the desired functions of reaction and distillation sites. To achieve this the structure must be such as to provide fairly uniform spatial distribution in the column.
A second criteria is that there must be sufficient free space in the catalyst bed to allow for the liquid phase surface contact and vapor phase distillation with the concurrent separation of the material in the column by the distillation into vapor and liquid phases. It has been observed that in the catalyst bed a free space of about 50 volume % is adequate to obtain an operable fractionation.
A third criteria is the necessity for the catalyst bed to be able to expand and contract as it must during use without undue attrition of the catalyst.
The present invention meets all of the criteria is a superior manner.